The invention relates to aqueous, buffered fluoride containing compositions having a pH of from greater than 7.0 to about 11.0. These compositions are used as resist and etch or ash residue removers and cleaners in the production of semiconductor devices. The buffered, fluoride containing compositions resist changes in pH and exhibit low corrosive effects on metal films such as aluminum, copper, titanium, tungsten and the like, and low oxide etch rates. More particularly, the invention relates to aqueous, buffered, fluoride containing compositions useful as resist and etch or ash residue removers and cleaners that use molecules not typically viewed as buffers. The buffers of the present invention include the use of a variety of weak acids or protonated bases which act as weak acids in solution that are effective over a pH range of greater than 7.0 to about 11.0. The invention also includes methods of preparing the fluoride containing compositions and their use.
There are a number of fluoride containing compositions disclosed in the art. Torii (U.S. Pat. No. 5,972,862) discloses fluoride containing compositions used as stripper-cleaners. Tanabe (U.S. Pat. Nos. 5,792,274 and 5,905,063) disclose resist remover compositions having a pH of from 5 to 8, containing metal-free salts of HF, a water soluble organic solvent, and optionally a corrosion inhibitor. Maruyama (U.S. Pat. No. 5,692,385) discloses a composition containing from 0.1 wt % to 10 wt % ammonium and alkyl ammonium salts of HF, from 72 wt % to 80 wt % of an organic solvent that is water soluble and the remainder water. According to the teachings in Maruyama, both the fluoride containing compound and the solvent must be present in the given ranges, otherwise the detrimental side effects such as corroding of substrates and poor performance occur. None of the above cited references recognize the effective use of buffers to improve the pH stability of fluoride containing compositions.